I've always had a soft spot for rats, which is why I raised many as pets during my college years. The heaps of rat anecdotes I possess are legion, but the most amusing could possibly be when Goya, my favored albino, had a staring match with my wife. Unfortunately, she didn't care for the fact the little furball knew how to get out of her cage.
Rats have personalities, and they can be glum or cheerful depending on their upbringing and circumstances. One study showed that rats accustomed to good times tend to be optimists, while those reared in unstable conditions become pessimists. Both rats will learn to associate one sound with a good event — a gift of food — and another sound with no food, but when exposed to an ambiguous sound, the optimist will run over expecting to be fed and the pessimist will grumble and skulk away, expecting nothing.
Too true. A rattle of potato chips was enough to drive my broods into quivering frenzy.